Inferential Statistics

All decisions based on inferential statistics are based on 4 criteria:

• Normality  of the scores
  • Type of sample group
  • Number of independent variables
  • Number of dependent variables

If variables are normally distributed, parametric forms of statistics are used.

If variables are not normally distributed, non-parametric forms of statistics are used.

• For correlation:
  •  Normally distribution use Pearson’s Correlation
  • Not normal distribution use Spearman’s correlation
  • For group comparisons:
  • Both parametric and non-parametric tests are dependent on the type of group
  • If sample groups which are to be compared are independent of each other then different statistic is used, and
  • If the sample group is the same, or related, such as that for pre-post intervention design, then a different group of statistic is used.

• Therefore, before deciding on a test, the researcher must look for three things:

1. Normality of the variable
2. If the sample groups are independent or related
3. Number of variables present